In recent years, as mobile communication terminals such as cellular phones have become more sophisticated, high-speed wireless communication has advanced. Since the communication speed is proportional to the bandwidth of the frequency to be used, the frequency band required for communication is increasing. Along with this, the number of installed high frequency filters required for mobile communication terminals has also increased.
Spintronics has been being studied as a field that can be applied to new high frequency components in recent years. One of the phenomena that is attracting attention in spintronics is a ferromagnetic resonance phenomenon of a magnetoresistance effect element.
When an alternating current or alternating magnetic field is applied to a ferromagnetic layer included in a magnetoresistance effect element, ferromagnetic resonance can be caused in the magnetization of the ferromagnetic layer. When ferromagnetic resonance occurs, the resistance value of the magnetoresistance effect element oscillates cyclically at the ferromagnetic resonance frequency. The ferromagnetic resonance frequency varies depending on the intensity of the magnetic field applied to the ferromagnetic layer, and its ferromagnetic resonance frequency is generally in a high frequency band of several to several tens of GHz.
For example, Japanese Unexamined Patent Publication No. 2017-063397 describes a magnetoresistance effect device usable as a high frequency device such as a high frequency filter utilizing the ferromagnetic resonance phenomenon.